Power generating device employing hydrogen absorbing alloy and low heat

ABSTRACT

A power generating device employing hydrogen absorbing alloy and low heat wherein two types of hydrogen absorbing alloys that can reversibly absorb and release hydrogen gas and have different thermal equilibrium hydrogen pressure characteristics are used and loaded, respectively, in a first hydrogen absorbing alloy heat exchanger container (1) and a second hydrogen absorbing alloy heat exchanger container (2) that are ventilably connected to each other, wherein at least two sets of heat generating cycles are provided that employ heat generated when hydrogen gas is moved between the first hydrogen absorbing alloy heat exchanger container (1) and the second hydrogen absorbing alloy heat exchanger container (2), wherein a low temperature side hydrogen absorbing alloy hydrogen compound that has a higher equilibrium hydrogen pressure at the same temperature is heated by low quality heat sources (8, 9, 10), wherein released hydrogen is absorbed by a high temperature side hydrogen absorbing alloy having a lower equilibrium hydrogen pressure to thereby obtain heat having a temperature that is higher than the temperature of the low quality heat sources, and wherein cooling medium vapour is generated by the heat so obtained so that power generation can be effected by a gas turbine (13).

TECHNICAL FIELD

This invention relates to a power generating device which convertsunused low quality heat energy having a temperature from 30° C. to 60°C. such as heat collected by solar energy collectors, heat ofterrestrial heat energy, warm waste water discharged from hot springs,waste heat discharged from factories and garbage destructors into heathaving a higher temperature from 80° C. to 90° C., and transmits theheat to a medium having a low boiling point for a vaporization so thatthus obtained vapour drives a turbine to generate power, and can beuniversally used as a system for converting unused energy to generatepower.

BACKGROUND OF ART

As one of prior power generating devices using a turbine, a deviceemploying power of a turbine driven by vapour of a heating medium isgenerally and universally used.

In such a power generating device employing a gas turbine, powergeneration can be effected in the manner that cooling medium vapour suchas steam, ammonia, fluorocarbon, or vapour obtained by vaporizingheating medium such as natural gas with heat is pressed and introducedinto the gas turbine to drive the gas turbine, discharged vapour fromthe gas turbine is cooled and condensed, and thus obtained liquid mediumis re-heated to be circulatively introduced into the gas turbine aspressed vapour. In the device, however, a temperature difference betweena heating temperature and a cooling temperature should be extremelygreat, namely 100° C. or greater. In fact, it is difficult to drive thegas turbine of the device with a heating source having a temperature ofabout 150° C. and a cooling source having a temperature from 10 to 30°C. due to extreme poor thermal efficiency and high cost of equipment.

A power generating device employing hydrogen absorbing alloys whichmakes use of power of a turbine driven with hydrogen gas has beendeveloped in these years.

In such a power generating device making use of a hydrogen gas turbine,power generation can be effected in the manner that a device loaded witha hydrogen compound of a hydrogen absorbing alloy is heated with a heatsource having a temperature from 300 to 350° C. to introduce releasedhydrogen having a high temperature and a high pressure so as to drivethe hydrogen gas turbine, and then discharged hydrogen from the hydrogengas turbine is introduced into another device loaded with a hydrogenabsorbing alloy and absorbed by the hydrogen absorbing alloy so that thedevice is also heated to circulatively introduce hydrogen having a hightemperature and a high pressure into the hydrogen gas turbine. Thedevice, however, has problems such that more hydrogen should be movedthan in a heat pump employing hydrogen absorbing alloy, and a heatingsource at a high temperature side should have a temperature from 300 to350° C., thereby a temperature to release hydrogen rises, thermalefficiency becomes very poor, employed hydrogen absorbing alloys aredeteriorated and declined in quality and durability, and cost ofequipment is increased.

The present invention is to solve the above mentioned problems of theprior power generating devices and has an object to provide aneconomical power generating device with high thermal conversionefficiency which can be used in various fields.

DISCLOSURE OF INVENTION

The present invention relates to a power generating device employinghydrogen absorbing alloys and low heat wherein two types of hydrogenabsorbing alloys that can reversibly absorb and release hydrogen gas andhave different thermal equilibrium hydrogen pressure characteristics areused and loaded, respectively, in a first hydrogen absorbing alloy heatexchanger container and a second hydrogen absorbing alloy heat exchangercontainer that are ventilably connected to each other, wherein at leasttwo sets of heat generating cycles are provided that employ heatgenerated when hydrogen gas is moved between the first hydrogenabsorbing alloy heat exchanger container and the second hydrogenabsorbing alloy heat exchanger container, wherein a hydrogen compound ofone of the hydrogen absorbing alloys at a low temperature side that hasa higher equilibrium pressure at the same temperature is heated by lowquality heat sources to release hydrogen, wherein the released hydrogenis absorbed by the other hydrogen absorbing alloy at a high temperatureside having a lower equilibrium hydrogen pressure to thereby obtain heathaving a temperature that is higher than the temperature of the lowquality heat sources, and wherein cooling medium vapour is generated bythus obtained heat so that power generation can be effected by a gasturbine. The present device enables to convert low temperature energywhich has not been utilized into high temperature energy employinghydrogen absorbing alloys to generate power, with the high temperatureenergy, efficiently. High temperature heat sources from 150 to 350° C.used in the prior power generations are no longer required for thepresent device due to its high thermal conversion efficiency so that thepresent device is extremely economical.

BELIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a power generating device employinghydrogen absorbing alloys and low heat relating to the presentinvention.

FIG. 2 is a table showing heat generation cycles to drive a powergenerating device employing hydrogen absorbing alloys and low heatrelating to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

One of preferable embodiments will be described hereinafter referring tothe drawings.

As shown in FIG. 1, the present power generating device employinghydrogen absorbing alloys and low heat mainly comprises hydrogenabsorbing alloy heat exchanger containers 1, 2, 3, 4 loaded with thehydrogen absorbing alloys, a low temperature heat storage tank 7, a hightemperature heat storage tank 11, a cooling medium vaporizer 12, a gasturbine 13 and a power generator 14.

Low quality heat sources (from 30 to 60° C.) such as heat 8 collected bysolar energy collectors, heat of terrestrial heat energy, warm wastewater 9 discharged from hot springs, low quality energy of waste heatdischarged from factories or warm waste water discharged from garbagedestructors, and exhaust gas 10 are stored in the low temperature heatstorage tank 7.

Two sets of two types of hydrogen absorbing alloys Ma, Mb havingdifferent thermal equilibrium hydrogen pressure characteristics whichare loaded respectively in two hydrogen absorbing alloy heat exchangercontainers are prepared. Namely, the hydrogen absorbing alloy Ma isloaded in the hydrogen absorbing alloy heat exchanger containers 2, 3,and the hydrogen absorbing alloy Mb is loaded in the hydrogen absorbingalloy heat exchanger containers 1, 4. The hydrogen absorbing alloy heatexchanger containers in each of the sets are connected to each other bymeans of a valve 5, 6 so that hydrogen gas can move thorough the valves.In the sets, the hydrogen absorbing alloy Mb has a higher equilibriumhydrogen pressure than that of the hydrogen absorbing alloy Ma at thesame temperature as shown in FIG. 2. In FIG. 1, 15 shows a mediumcondenser, 16 shows a tank, 17 shows a medium feed-back pump, 18 shows apreheater, and 19 and 20 show cooling water.

How the power generating device comprises as described above is operatedwill be described hereinafter.

The hydrogen absorbing alloy Mb in the hydrogen absorbing alloy heatexchanger container 1 at a low temperature side having a higherequilibrium hydrogen pressure absorbs hydrogen to become a metallichydrogen compound MbH. The hydrogen absorbing alloy heat exchangercontainer 1 is heated with low temperature water of 40° C. obtained fromunused low quality heat sources 8, 9, 10 in the heat storage tank 7,resulting in an endothermic reaction of the metallic hydrogen compoundMbH to release hydrogen since pressure inside the hydrogen absorbingalloy heat exchanger container 1 is increased. The released hydrogen ismoved to the hydrogen absorbing alloy heat exchanger container 2 to beabsorbed by the hydrogen absorbing alloy Ma at a high temperature sidehaving a lower equilibrium hydrogen pressure. Then an exothermicreaction occurs to release high temperature heat of 80° C. to generatehot water which is stored in the high temperature storage tank 11. Thusheat having a high temperature can be obtained from heat having a lowtemperature. The cooling medium vaporizer 12 is heated with the hotwater to vaporize the medium so that so obtained vapour drives turbine13 to generate power 21 at the power generator 14.

While, in a recycling process, a metallic hydrogen compound MaH in thehydrogen absorbing alloy heat exchanger container 3 is heated with lowtemperature water of 40° C. in the low temperature heat storage tank 7resulting in an endothermic reaction to release hydrogen, since apressure inside the hydrogen absorbing alloy heat exchanger container 3is increased. The released hydrogen gas falls in temperature to the airoutside of 20° C., and is moved to the hydrogen absorbing alloy heatexchanger container 4 having a decreased pressure so that the hydrogenabsorbing alloy Mb at a low temperature side having a higher equilibriumhydrogen pressure absorbs the released hydrogen gas to become again ametallic hydrogen compound MbH so as to repeat the cycle.

As described above, by employing at least two sets of hydrogen absorbingalloys Ma and Mb, high temperature heat can be successively generatedand a uniform amount of hydrogen gas can be repeatedly moved between thehydrogen absorbing alloys Ma and Mb with no loss. The present powergenerating device can be successively driven by heating the coolingmedium vaporizer with the successively generated high temperature heat,vaporizing the medium and driving the turbine with the vapour.

As the hydrogen absorbing alloys Ma and Mb, hydrogen absorbing alloyshaving different equilibrium hydrogen pressures are used. To put itconcretely, rare earth hydrogen absorbing alloys are favorably combinedand used, for example, LaNi_(5-x) Al_(x), MmNi_(5-x) Al_(x), MmNi_(5-x)Mn_(x), MmNi_(5-x) Al_(X-Y) Mn_(Y) (0<X≦1.0, 0<Y≦0.5) can be used as thehydrogen absorbing alloy Ma, and LaNi₅, MmNi_(5-x) Al_(x), MmNi_(5-x)Mn_(x) (0<X≦1.0) can be used as the hydrogen absorbing alloy Mb,however, there is no restriction for the hydrogen absorbing alloys. Theabove mentioned Mm means Misch metal which is a mixture of rare earthmetals.

The following table shows one example of principal conditions to operatethe present power generating device employing hydrogen absorbing alloysand low heat.

    ______________________________________                                        AMOUNT OF GENERATED POWER                                                                              100 KW                                               AMOUNT OF GENERATED HEAT 250 KW                                               KIND OF HYDROGEN ABSORBING ALLOY                                                                       RARE EARTH                                                                    HYDROGEN                                                                      ABSORBING                                                                     ALLOYS                                               AMOUNT OF HYDROGEN ABSORBING ALLOY                                                                     10,000 KG                                            AMOUNT OF HYDROGEN       850 Nm.sup.3                                         THERMAL CONVERSION EFFICIENCY                                                                          70%                                                  TEMPERATURE OF           80-90° C.                                     HIGH TEMPERATURE HEAT SOURCE                                                  TEMPERATURE OF           30-60° C.                                     LOW TEMPERATURE HEAT SOURCE                                                   ______________________________________                                    

INDUSTRIAL APPLICABILITY

The present power generating device employing hydrogen absorbing alloysand low heat can convert low quality (low temperature) heat energy suchas solar energy, terrestrial heat energy, energy from factories andgarbage destructors into high quality (high temperature) heat byemploying hydrogen absorbing alloys and enables to generate powerefficiently with the heat so that the present invention can reduceconsumption of oil and contribute to preserve the earth environment.

What is claimed is:
 1. A power generating device employing hydrogenabsorbing alloy and low heat and further comprising:two types ofhydrogen absorbing alloys which are able to reversibly absorb andrelease hydrogen gas and which have different thermal equilibriumhydrogen pressure characteristics; said two types of hydrogen absorbingalloys loaded respectively in a first determined hydrogen absorbingalloy heat exchanger container and a second determined hydrogenabsorbing alloy heat exchanger container which are connected ventably toeach other; at least two sets of heat generating cycles which employheat generated when hydrogen gas is moved between said first and secondhydrogen absorbing alloy heat exchanger containers provided; a hydrogencompound of one of said hydrogen absorbing alloys at a low temperatureside having a higher equilibrium pressure at the same temperature isheated by at least one low quality heat source having a temperature from30° to 60° C. to release hydrogen; said released hydrogen absorbed bythe other hydrogen absorbing alloy at a high temperature side having alower equilibrium hydrogen pressure to generate heat having atemperature from 80° to 90° C. which is higher than the temperature ofthe low quality heat source; said heat is transmitted to a coolingmedium vaporizer to generate cooling medium vapour; and where power isgenerated by a gas turbine driven by pressure of said cooling mediumvapour.
 2. A power generating device as set forth in claim 1 whereinsaid hydrogen absorbing alloy is selected from the group consistingof:MmNi_(5-x) Al_(x) ; MmNi_(5-x) Mn_(x) ; MmNi_(5-x) Al_(x-y) Mn_(y) ;where (0<X≦1.0, 0<Y≦0.5) is used as said hydrogen absorbing alloy.